Prevention of pitting of steam boilers



Jan. 28, 1941.

J. W. SCHMID PREVENTION OF FITTING 0F STEAM BOILERS Filqd Jan. $50, 1939 2 Sheets-Sheet 2 Patented Jan. 28, 1941 PREVENTION OF PITTING OF STEAM BOILERS Julian W. Schmid, Springfield, Mo. Application January 30, 1939, Serial No. 253,665

5 Claims.

This invention relates to steam boilers and more particularly to a means for preventing pitting within the boiler.

An object of this invention is to provide an at- 5 tachment which may be mounted within the interior of the boiler which will provide a means for raising the pH of the feed water within the boiler so as to substantially eliminate pitting.

Under recognized principles of water treatment for boiler use there is an excess of alkalinity over hardness or scale forming salts. When the water is properly treated, the hardness that remains in the feed water is precipitated in the boiler in the cess alkalinity concentrates in the boiler and at the higher temperature inside the boiler part of the carbonate excess is converted into caustic soda. In a boiler carrying 200 lbs. gauge pressure, this carbonate excess continues until '75 or 80% is caustic soda and 20 or 25% is sodium carbonate. While it is possible to treat water for boiler use and raise its pH value above the pitting point before it enters the boiler, thus preventing pitting, this is not always practical or even desirable, as when water with low hardness and dissolved solids and low pH is treated with device with the caustic soda of the boiler water forming normal sodium carbonate. carbonate is discharged from the trough intothe boiler where it is slowly converted until '75 or 80% is caustic soda. Anydissolved oxygen that may be in the feed-water is driven 011" in the trough and is carried from the boiler with the'steam. In

the ordinary method of putting feed water into a. boiler, especially Where there is a small amount of circulation of water in the boiler, as in the case of a locomotive when it is standing still and the pH of the feed water is below the pitting point, the mixture of the feed water in the-boiler water is not sufficient to prevent pitting without using excessive treatment. This is shownby the form of a soft sludge that does not adhere to the boiler parts and does not form scales." The ex- With this invention only areadily combines in the pipe and trough of this- This normal fact that when there is pitting in a boiler most of it is near the point where the feed water enters the boiler and in the path and direction of circulation of -the feed water after it enters the boiler.' As the feed water mixes with the boiler water, the pH is raised and the pitting diminishes. This invention by thoroughly mixing the boiler water with the feed water uses the caustic soda of the boiler water to raise the pH of the resulting mixture above pitting point before it comes in contact with the metal parts of the boiler. I

A further object of this invention is to provide a mixing device of this kind whereby the hardness or scale forming salts are precipitated in-a solution of higher pH value, thus forming a better floc and obtaining a. more complete precipitation of scale forming salts, particularly near the point where the feed water enters the boiler.

A stillfurther object of this invention is to provide a device of this kind to lessen the danger of caustic embrittlement; this accomplished be-, cause a smaller excess can be carried in the boiler water and the caustic content is reduced by combining with, the CO2 liberated from the bicarbona'tes and the free CO2 of the feed water.

A still further object of this invention is to reduce foaming. This will result from the fact that a smaller amount of chemicals will be added to the water thus reducing the dissolved solids in so the boiler water. Also, the better fioc obtained and the. better mixture throughout the boiler will allow a higher concentration of dissolved solids in the boiler, thus causing less foaming.

A further object of this invention is to provide in a .mixing device of this kind means whereby the combined'boiler and feed water is agitated duringthe discharge of the combined water within the interior of the boiler. I

A further object of this invention is to provide 40 a device of this kind which acts as a preheating means for the incoming feed water so as to substantially eliminate all strain or stress on the boiler by. reason of the reduced temperature of the incoming feed water.

To the foregoing objects and to others which may hereinafter appear. the invention consists of the novel construction, combination and arrangement of parts as will be more specifically referred to and illustrated in the accompanying drawings wherein is shown an embodiment of the invention, but it is to be understood that-changes. variations and modifications may be resorted to which fall within'the scope of the invention as claimed. V g 5E In the drawings:

Figure 1 is a fragmentary longitudinal section of a conventional tube boiler having an antipittingdevice constructed according to an embodiment of this invention mounted therein,

Figure 2 is a horizontal section taken substantially on the line 2--2 of Figure 1,

Figure 3 is a fragmentary plan view of the mixing trough positioned within the boiler,

Figure 4 is a longitudinal section taken on the line 4-4 of Figure 3,

Figure 5 is a sectional view taken on the line 5-5 of Figure 3,

Figure 6 is a sectional view taken on the line 6-6 of Figure 3, and I Figure '7 is a sectional view taken on the line I Referring to the drawing and first to Figures 1, 2, and 6 to 11 inclusive, the character B designates generally a boiler structure which is provided with a plurality of tubes T which are mounted in plates l5 and IS. The plate l5 forms above the top of the crown sheet ll.

In order to provide a means whereby the pH content of the boiler may be maintained at a point above the pitting point, I have provided a trough member generally designated as 2| which is mounted interiorly of the boiler B between the rear end of the crown sheet I! and the plate member l6 forming the inner wall of the smoke box I8. The trough 2| is pr ferably suspended from the boiler B by means ohangers or bracket members 22 which are secure to the wall of the boiler B and to the sides of the trough 2|. The trough 2|, as shown in Figures 6, '7, 9, 10 and 11, is substantially U'-shaped in transverse section and is provided with open opposite end portions.

The trough member 2| comprises a substantially V-shaped bottom wall or bight 23 and upstanding side walls 24. The bottom wall 23 forms a longitudinally extending ridge within the trough 2| and in the peak of the bottom 23 a plurality of longitudinally spaced apart openings 25 are provided. The openings 25, are provided for the purpose of admitting steam from the upperportion of the boiler B into the water which is flowing through the trough 2|. In this manner, the rising steam will act as a preheating means for incoming feed water and will also serve as an agitating means so as to thoroughly agitate the incoming feed water.

The trough 2| at a point inwardly from the discharge end 26 thereof is provided with a pair of inwardly directed plates 21 which are struck from the vertical walls 24 and form opposite outlet openings 28. These inwardly projecting wall portions 21 are bent or extended inwardly as shown in Figure 6 to a point intermediate the outer wall 24 and the center of the bottom of the trough in order that these extensions 21 will only out ed a portion of the water flowin through the trough 24 and discharge thiscut off water into the main boiler water ahead of the discharge opening 26. In this manner, the in- "coming feed water is distributed into the boiler.

water at several points, thus eliminating the concentration of any solids at one particular point as is at present the case.

The trough 2| has an open'intake end.29 in which a feed water discharge pipe 3| engages. The pipe 3| is open at'its inner end and is dithe incoming feed water will be forced longitudinally of the trough 2| The feed pipe 3| is connected at its outer end to a housing 32 which is substantially semi-spherical in configuration and is provided with a plate 34 having a marginal flange 35. The housing 32 is adapted to be secured to the inner side of the boiler B and a water discharge nozzle 36 extends through a boss 31 carried by the plate 34 and is adapted to be connected to a suitable source of'feed water supply remote from the boiler B. The inner end of the nozzle 36 is positioned axially of the adjacent end of the pipe 3| and is relatively smaller in diameter at its discharge end than the inner end of the pipe 3|. An inwardly opening check valve 38 is interposed in the pipe 39 which is connected to the nozzle 36 and is adapted to prevent rearward movement of the water under the pressure of steam generated within the boiler B.

A boiler Water pipe 40 is connected at one end to the mixing housing 32 and the other or inner end of the boiler water pipe 40 is provided with a downwardly directed intake member 4| which is positioned closely adjacent the inner end of" the crown sheet H. The open end of the intake member 4| is directed downwardly and is positioned slightly below the normal water level in the boiler, as shown by the dot and dash line 20.

In tne use and operation of this device, the pipe 39 is connected'at one end to a source of feed water supply and the trough 2| is mounted by the hangers 22 within the boiler B with the open end of the trough 2| directed upwardly and preferably positioned with the upper edges of the trough 2| disposed slightly above the normal water level of the water in the boiler B. The incoming feed water is discharged under pressure in the mixing member 32 through the nozzle 36 which will form a suction so as to raw in boiler water through the intake member 4| and the pipe 40. The boiler water is thus mixed with the chemically treated. feed water and then discharged in the open trough 2|. The water in the boiler B will bubble up through the openings 25 and this bubbling water which is also partly steam will mix with the incoming feed water so as to raise the temperature of the incoming water and at the same time thoroughly agitate the in "of the solids at the inner end of the feed water trough 2|.

With a device of this kind, it is not necessary to treatthe boiler water or feed water with caustic soda, soda ash, or other chemicals in order to raise the pH content above the pitting point. This latter procedure increases the concentration of solids in the boiler which thereby necessitates frequent blowing outof the boiler water. However, with a device as hereinbefore described, the chemically treated incoming feed water is mixed with a small quantity of boiler water and the mixture during the discharge thereof in the rectedlongitudinally of the trough 2| so that boiler water is so agitated that the temperature of the incoming feed water will be quickly raised and in this manner, the incoming feed water will not cause a pitting within the boiler as is at present the case.

What I claim is:

1. In a boiler, means to prevent pitting on the interior of the boiler, comprising an open ended trough, means supporting the trough in the boiler with at least a portion of the trough above the normal water level, and means for discharging feed water in an end of said trough, said trough having an upwardly offset bottom wall provided with'a plurality of longitudinally spaced apart openings whereby steam is admitted within the trough at spaced intervals to thereby agitate the feed water in the trough and simultaneously raise the temperature of the feed water.

2. In a boiler, means to prevent pitting on the interior of the boiler, comprising an open ended trough, means supporting the trough in the boiler with at least a portion of the trough above the I normal water level, and means for discharging feed water in an end of said trough, said trough being substantially U-shaped in transverse section and provided with a plurality of spaced apart openings in the bight thereof.

3. In a boiler, means to prevent pitting on the interior of the boiler, comprising an open ended trough, means supporting the trough in the boiler with at least a portion of the trough above the normal water level, and means for discharging feed water in an end of said trough, said trough having an inwardly projected bottom wall providing a longitudinal channel on the underside thereof, and said trough having a plurality of spaced apart openings in the bottom wall.

4. In a boiler, a trough open at each end and at the top thereof, means supporting said trough in said boiler, means discharging feed water into said trough, said trough including vertical side vwalls and a bottom wall, said trough having a plurality of openings in the bottom thereof, and inwardly extending means carried by the vertical walls of said trough between the ends thereof for by-passing a quantity of the feed water in said trough into the boiler water, the dissolved oxygen and CO2 within the trough rising upwardly of said side walls for' commingling with the steam above the trough.

5. In a boiler, an open trough, means supporting said trough in said boiler, means discharging feed water into said trough, said trough being substantially U-shaped in transverse section with the bight thereofhaving the configuration of an inverted V, said trough having openings in the apex of the v, and inwardly projecting by-pass members carried by the side walls ofthe trough.

JULIAN W. SCHMID. 

